Electrophotographic photoreceptors of the function separation type have been proposed which are provided with a charge generating layer and a charge transporting layer. In recent years, such electrophotographic photoreceptors have been used not only in electrophotographic copying machines, but also printers utilizing such light sources as semiconductor lasers, light emitting diodes, etc. It is therefore strongly desired to develop a charge generating material having broad spectral sensitivity extending from the visible to the infrared region of the spectrum (400 to 800 nm).
Various charge generating materials have hitherto been proposed. However, there is no single charge generating material that satisfies the above requirement. JP-B-59-32788 (the term "JP-B" as used herein means an "examined Japanese patent publication") proposes to use in the charge generating layer at least two pigment or dyes having different spectral sensitivity characteristics (phthalocyanine dyes are used for longer wavelength regions).
However, electrophotographic photoreceptors utilizing two or more pigments or dyes having different spectral sensitivity characteristics suffer from the disadvantage that their sensitivity markedly drops locally, as shown, e.g., in FIG. 2 which depicts spectral sensitivity curves (the ordinate axis: sensitivity 1/E 1/2) B: N,N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide, C: metal-free phthalocyanine, and A: wherein B and C are used in combination at a ratio (B/C) of 97/3 (an example shown in JP-B-59-32788). The figure indicates that the combined use of two pigments fails to provide a sufficient overall sensitivity because of the significant local decrease in sensitivity. In addition, it also suffers from the disadvantage that electrophotographic characteristics such as electrification property and dark decay, also change to a considerable extent.